ICEBERGS 309 



alone. Luckily the Barrier may be subjected to further calcula- 

 tion, being in the happy position of a mass of ice resting on a 

 frictionless plane at freezing-point. Thus with certain assump- 

 tions regarding the rather uncertain coefficient of viscosity of ice 

 and a slight excursion into integral calculus, we can arrive at the 

 conclusion that the Barrier under its own weight would each 

 year push out a distance of from 100 to 500 yards, a distance 

 at least of the same order of magnitude as that found by 

 observation. 



From this we see we are probably justified in neglecting the 

 volume of ice added to the Barrier and carried down by glaciers 

 from the plateau and may treat the Barrier as an entity by itself. 



Consider now the effect of such a Barrier in equilibrium, en- 

 closed on three sides and exposed to a continuous snowfall. 

 Without any further mathematics it is at once clear that the 

 velocity of motion at the seaward edge must be very many times 

 faster than the velocity at the shore farthest from the sea. The 

 tendency of a continuous snowfall would be therefore to accumu- 

 late a much greater thickness of Barrier on the side farthest from 

 the sea. That this is not so, is shown by the barometric observa- 

 tions of the sledging parties, which furnish convincing proof that 

 the Barrier is still afloat quite close to the landward end, and 

 further that a very good current circulation obtains under this 

 part, since the single circumstance capable of preventing an accu- 

 mulation of snow, is a corresponding melting action, which again 

 can only be due to water underneath the Barrier. 



ICEBERGS 



It has been noted that the Barrier and also land-glaciers may 

 discharge ice into the sea in the form of bergs. Since no bergs 

 were ever seen in McMurdo Sound except in the late summer 

 months it may almost be taken that the prime cause of the calv- 

 ing of bergs from the parent glacier is due to the melting action 

 of the warm sea water. 



Bergs met with in the Antarctic can best be roughly divided 

 into barrier or tabular bergs and glacier bergs. The tabular berg 

 is recognised by its flat tabular form, whereas the glacier berg 

 seldom has such a regular profile and often is formed of deep 

 blue ice in contradistinction to the dazzling whiteness of the 



